Abstract: An air-regulation device is combined into a single subassembly along with a pneumatic switch that activates a circulating pump associated with a bathtub. The common housing has air channels that open into connector bushings on a connector. The inlets to the air channels can be closed or opened by means of a control knob with a kidney-shaped air passage. The piston of the pneumatic switch is mounted in such a way as to slide within a chamber in the center of the housing. The piston is activated by means of a disk positioned in a recess in the knob. Air flows around the disk in all operating positions.